• Advances in Computational Design
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• 제7권4호
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• pp.371-393
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• 2022

This paper presents a three-dimensional flexible pavement simulated in ANSYS subjected to moving vehicular load on the surface of the pavement typical for the road section in Nepal. The adopted finite element (FE) model of pavement is validated with the classical theoretical formulations for half-space pavement. The validated model is further utilized to understand the damping and dynamic response of the pavement. Transient analysis of the developed FE model is done to understand the time varying response of the pavement under a moving vehicle. The material properties of pavement considered in the analysis is taken from typical road section used in Nepal. The response quantities of pavement with nonlinear viscoelastic asphalt layer are found significantly higher compared to the elastic pavement counterpart. The structural responses of the pavement decrease with increase in the vehicle speed due to less contact time between the tires of the vehicle and the road pavement.

• 한국지반환경공학회 논문집
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• 제13권9호
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• pp.61-68
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• 2012

본 연구의 주된 목적은 EPS지오폼이 연성포장의 노반재료로 사용될 때 그것의 회복탄성계수를 해석 모델화 하는 것이다. 이 해석모델은 삼축압축 시험으로부터 나온 실험결과를 토대로 만들어졌다. 그리고 이 모델은 원하는 용도에 따라서, 기존의 프로그램을 수정하거나 새로 개발하여 유한요소법을 이용한 연성포장구조를 해석하는데 사용될 수 있다. 또한 본 연구의 결과는 연성포장에서의 현장 연약지반 노상재료의 대체물로서 EPS지오폼은 적합한 것으로 확인되었다.

• Structural Engineering and Mechanics
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• 제6권7호
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• pp.817-826
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• 1998

A finite element model based on the incremental endochronic theory for flexible pavement materials was developed in this study. Three grid systems with eight-node cubic isoparametric elements, and different loading steps were used to perform the calculations for a specimen of circular cylinder. The uniaxial stress experimental results on an asphalt mixture at $60^{\circ}C$ in SHRP conducted by University of California at Berkeley were used to check the ability of the derived numerical model. Then, the numerical results showed isotropic response and deviatoric response on the specimen in a three dimensional manner, which provided a better understanding for a deformed flexible material under the specified loading conditions.

• Geomechanics and Engineering
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• 제32권1호
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• pp.35-47
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• 2023

Deformability of road pavements in the form of ruts represent a safety risk for road users. In the procedures for dimensioning the pavement structure, the requirement that such deformations do not occur is imperatively included, which results in the appropriate selection of elements (material, geometry) of the pavement structure. Deformability and functionality, will depend of the correct design of pavement structure during exploitation period. Nevertheless, there are many examples where deformations are observed on the pavement structure, in the form of rutting at parts of the road with relatively short length, realised in the same climatic and the same geoenvironmental conditions. The performed analysis of deformability led to the conclusion that the level of deformation is a function of the speed of traffic. This effect is observed on city roads, but also outside of urban areas at roads with speed limits are significant, due to the traffic management, traffic jams (intersections, etc.). Still, the lower speed cause greater deformations. The authors tried to describe the deformability of flexible pavement structures, from the aspects of geotechnical problems, as a function of driving speed. Outcome of the analysis is a traffic load correction coefficient, in terms of using the existing methods of flexible pavement structures design.

• 한국도로학회논문집
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• 제10권4호
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• pp.213-224
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• 2008

트럭 축하중에 의한 도로포장체의 응력과 변형은 대부분 다층 탄성 이론에 의해 예측된다. 대부분의 다층 탄성 이론에 의한 이론적 계산값이 연성 포장 재료의 점탄성적 거동특성, 동적 트럭 축하중, 비균등 타이어 접지압 및 형상등을 해석에 고려하지 못하므로, 계측값에 비해 매우 작은 값을 예측하므로서 도로 포장 두께설계가 과소 설계될 우려가 크다. 이와 같은 도로 포장체 구조해석시 이용되는 중요한 변동요소를 포장 재료의 물성 모델 측면, 비균등 접지압 및 형상 측면, 동적 유한요소해석 측면에서 분석하여 이용 가능한 모델을 본 논문에서 제안하였다. 경계조건 및 민감도 분석을 수행을 통한 효과적인 3차원 연성포장의 유한요소해석모델을 결정하는 방법론을 제안하였으며, 최적 유한요소모델 분석결과와 현장에서 취득한 결과와의 상호비교를 통하여 모델의 유의성을 검증하였으며, 동적 접지하중조건, 점탄성물성 모델 등을 3차원 유한요소 모델에 접목하고, 최적 경계조건을 결정하였다.

• 한국지반신소재학회논문집
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• 제14권2호
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• pp.35-44
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• 2015

본 연구의 연성포장설계의 해석적 연구를 위해 연성포장설계에 이용되는 EPS 지오폼 회복탄성계수 모델이 고안되어 노상층이 EPS 블럭인 연성포장의 수직방향 변형크기를 예측하기위한 프로그램인 RMEG 에 이용되었다. RMEG 프로그램은 EPS 지오폼의 노상층이 설계된 기한동안 얼마나 침하 하는지와 AASHTO 연성포장설계방정식에 의해 평가된 신뢰도 70%로 주어진 교통하중에 도로구조체가 얼마나 오랫동안 심각한 도로파손 없이 지탱하는지를 보여주었다. 그 결과, EPS 노상층의 예측 수직변형은 20.6년 동안 5mm 이하로 EPS 지오폼은 일반토사의 대체물로써 하자가 없음을 나타냈다.

• 한국도로학회논문집
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• 제17권1호
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• pp.69-75
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• 2015

PURPOSES : The objective of this study is to evaluate the effectiveness of a geogrid reinforced subbase of permeable flexible pavement structures with respect to permanent deformation. METHODS : Experimental trials employing a repeated triaxial load test scheme were conducted for both a geogrid reinforced subbase material and a control specimen to obtain the permanent deformation properties based on the VESYS model. Along with this, a finite element-based numerical analysis was conducted to predict pavement performance with respect to the rutting model incorporated into the analysis. RESULTSAND CONCLUSIONS : The results of the experimental study reveal that the geogrid reinforcement seems to be effective in mitigating permanent deformation of the subbase material. The permanent deformation was mostly achieved in the early stages of loading and then rapidly reached equilibrium as the number of load applications increased. The ultimate permanent deformation due to the geogrid reinforcement was about 1.5 times less than that of the control specimen. Numerical analysis showed that the permeable, flexible pavement structure with the geogrid reinforced subbase also exhibits less development of rutting throughout the service life. This reduction in rutting led to a 20% decrease in thickness of the subbase layer, which might be beneficial to reduce construction costs unless the structural adequacy is not ensured. In the near future, further verification must be conducted, both experimentally and numerically, to support these findings.

• Advances in Computational Design
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• 제3권2호
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• pp.201-212
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• 2018

Decrease in availability of suitable subbase and base course materials for highway construction leads to a search for economic method of converting locally available troublesome soil to suitable one for highway construction. Present study insights on evaluation of benefits of stabilization of subgrade soils in term of extension in service life (TBR) and layer thickness reduction (LTR). Laboratory investigation consisting of Atterberg limit, Compaction, California Bearing Ratio, unconfined compressive strength and triaxial shear strength tests were carried out on two types of soil for varying percentages of stabilizers. Vertical compressive strains at the top of unstabilized and stabilized subgrade soils were found out by elastoplastic finite element analysis using commercial software ANSYS. The values of vertical compressive strains at the top of unstabilized and stabilized subgrade, were further used to estimate layer thickness reduction or extension in service life of the pavement due to stabilization. Finite element modeling of the flexible pavement layered structure provides modern technology and sophisticated characterization of materials that can be accommodated in the analysis and enhances the reliability for the prediction of pavement response for improved design methodology. If the pavement section is kept same for unstabilized and stabilized subgrade soils, pavement resting on lime, fly ash and fiber stabilized subgrade soil B will have service life 2.84, 1.84 and 1.67 times than that of unstabilized pavement respectively. The flexible pavement resting on stabilized subgrade is beneficial in reducing the construction material. Actual savings would depend on the option exercised by the designer for reducing the thickness of an individual layer.

• 한국지반환경공학회 논문집
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• 제12권12호
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• pp.63-70
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• 2011

EPS지오폼은 다양한 강도, 밀도, 그리고 크기로 생산되는 일종의 화학합성물이다. EPS지오폼에 관한 근래의 발전으로 인해서, 그것의 사용은 급격하게 늘어나고있다. 이것은 초경량 재료로서 단위중량이 약 $0.16{\sim}0.47kN/m^3$ 인데, 이것은 채움재의 용도로 가장 대표적인 흙의 단위중량 $6.3{\sim}15.7kN/m^3$와 동일한 내구성을 가진다. 이런 장점에도 불구하고, EPS지오폼에 대한 회복탄성계수 표준측정방법은 보고된 바가 없는 실정이다. 본 연구의 주된 목적은 연성포장의 노반에 적용될 때의 EPS회복탄성계수의 적합성을 연구하는 것이다. 적합성연구는 삼축압축시험의 결과를 토대로 이루어졌으며, 연성포장의 노반재료로써 EPS는 실험결과의 분석과 근본적인 회복탄성의 특성을 비교분석하여 그것의 적합성을 확인해 보았다.

• 한국도로학회논문집
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• 제17권1호
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• pp.25-33
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• 2015

PURPOSES : This paper, presents the results of a laboratory study aimed to verify the suitability of a particular type of Electric Arc Furnace (EAF) steel slag to be recycled in the lithic skeleton of both dense graded and porous asphalt mixtures for flexible pavements. METHODS : Cyclic creep and stiffness modulus tests were performed to evaluate the mechanical performance of three different asphalt mixtures (dense graded, porous asphalt, and stone mastic) prepared with two types of EAF steel slag. For comparison purposes, the same three mixtures were also designed with conventional aggregates (basalt and limestone). RESULTS : All the asphalt mixtures prepared with EAF steel slag satisfied the current requirements of the European standards, which support EAF steel slag as a suitable material for flexible pavement construction. CONCLUSIONS : Based on the experimental work, the use of waste material obtained from steel production (e.g. EAF steel slag) as an alternative in the lithic skeleton of asphalt mixtures can be a satisfactory and reasonable choice that fulfills the "Zero Waste" objective that many iron and steel industries have pursued in the past decades.